A prominent Canadian-Iranian scholar who was studying women in the Muslim world has been arrested in Iran, highlighting the continued risk that dual nationals face when they travel to the Islamic Republic.

Homa Hoodfar, an anthropologist at Concordia University in Montreal, was first detained in March 10 by an intelligence unit of Iran’s Islamic Revolutionary Guard Corps, The New York Timesreported[1]. She was later released but not allowed to leave Iran, then arrested again last week and sent Tehran’s notorious Evin prison, according to her family.

“In recent months, the unit that arrested Ms. Hoodfar has questioned dozens of people with two nationalities and arrested several,” the Times noted.

Dual nationality is not recognized by Iran, and the regime denies arrested Iranians access to the consular offices of other countries they are citizens of.

Dual nationals currently held in Iran include businessman Siamak Namazi[2] and his father, Baquer Namazi, both of whom have American and Iranian citizenship. At least two British-Iranians — Nazanin Zaghari-Ratcliffe, an employee of Thomson Reuters, and businessman Kamal Foroughi — have also been arrested, as has Nizar Zakka[3], a Lebanese national with U.S. permanent residency.

The Times cited speculation that the dual nationals are being held as bargaining chips for future swaps.

Iran released five imprisoned American-Iranians in January just as the United States transferred $1.7 billion to the country, raising[4] concerns that the payment was a ransom. The $1.7 billion, which came from a U.S. taxpayer-supported fund, was appropriated[5] to supplement Iran’s expanding military budget.

A number of expatriate Iranian artists have criticized Iranian President Hassan Rouhani for failing to live up to his promise of allowing Iranian dual nationals to return to their country without fear.